|The Acorn 6502 Microcomputer Kit||Nick Brown recalls...|
Timeline & people
Using the Monitor
From: Nick Brown (nick.brown at free.fr) Date: 2006.03.28
Just came across your Acorn System 1 page – what nostalgia!
I had one back in 1979 – I had just taken a step back after receiving a battering in my first-year Engineering exams, and changed to the brand-new 2-year Computer Science part II.
Only problem was, I couldn’t get my head round assembly language, having been brought up on Fortran and Algol68... worlds where there was a runtime system to do everything for you. So I decided this was the way to learn it. I scraped some money together, bought the kit, soldered it together (this I could manage, at least), and set to work.
After about three months I started to get it. After six, I knew the disassembly of the ROM more or less by heart.
My proudest moment was when I identified a bug. Sometimes when I pressed the reset button, the rightmost digit of the display wouldn't be cleared – it would retain its original value across the reboot.
After much searching I established that a bit in the ROM was floating from 1 to 0 when the board warmed up. This meant that the counter which was used to count from 7 down to 0 across the display, started at 6 (fortunately, it was the least significant bit of a literal data byte which flipped, not the middle of a major instruction!). I took the board back and someone (it might well have been Chris Curry) replaced the ROM for me.
The System 1 turned up as the basis for a lab exercise over several weeks of my course. I was usually finished and in the bar within 20 minutes. :-) Some people who I rated pretty highly had real trouble understanding things at this basic level, which really encouraged me to work hard – and I got a first, to my total amazement.
Thanks for giving me the chance to relive those great days.